Article 9 — Relations between air navigation service providers

1. Without prejudice to Article 7(4) of this Regulation, air navigation service providers may avail themselves of the services of other service providers that are certified or that declared their capability in accordance with Article 41 of Regulation (EU) 2018/1139. Such cooperation shall be made in accordance with Article 11 of this Regulation where applicable. For air traffic service providers designated in accordance with Article 8 and MET providers designated in accordance with Article 10, such cooperation shall be subject to the authorisation of the Member States concerned. 2. For the purpose of paragraph 1, air navigation service providers shall formalise their working relationships by means of written agreements or equivalent legal arrangements, setting out the specific duties, including any financial settlements applicable, and the functions assumed by each provider. Those agreements or arrangements shall be notified to the national supervisory authority and the national competent authority concerned.